Hepadnavirus core antigens have been developed as a vaccine carrier platform (Billaud et al., J Virol, 79:13656-13666, 2005, and as a drug delivery vehicle (Beterams et al., FEBS Lett, 481:169-176, 2000; and Lee and Tan, J Virol Methods, 151:172-180, 2008). The purpose of a vaccine carrier platform is to provide the structural and immunologic framework to enhance the immune responses to heterologous B and/or T cell epitopes inserted therein. The more focused the immune response is on the heterologous epitopes and the less on the endogenous B cell epitopes of the carrier, the better. Carrier-specific antibodies may impede the immunogenicity of the heterologous epitopes and may attenuate the response in individuals who receive vaccinations at different times for different pathogens based on the same carrier (Renjifo et al., J Immunol, 161:702-706, 1998).
Thus what the art needs are vaccine carrier platforms with diminished carrier-specific antigenicity. In particular, hepadnavirus core antigens engineered to possess fewer endogenous B cell epitopes are desirable.